The president of Switzerland stepped to a podium in Bern last May and read a statement confirming rumors that had swirled through the capital for months. The government, he acknowledged, had indeed destroyed a huge trove of computer files and other material documenting the business dealings of a family of Swiss engineers suspected of helping smuggle nuclear technology to Libya and Iran.
Behind that official explanation, though, is a far more intriguing tale of spies, moles and the compromises that governments make in the name of national security.
The United States had urged that the files be destroyed, according to interviews with five current and former Bush administration officials. The purpose, the officials said, was less to thwart terrorists than to hide evidence of a clandestine relationship between the Tinners and the C.I.A.